Photodynamic therapy involves the use of a light activated compound which localizes in tumor, followed by the activation of this compound by light for cytotoxic effects for the treatment of cancer. The current protocol uses the intravenous administration of the Photofrin II preparation of the hematoporphyrin derivative. the only currently approved photosensitizer for use in humans. This is followed by the delivery of light to the affected area. Light is directed at the tumor using optical fibers coupled to a argon/pumped dye laser. Hematoporphyrin derivative selectively localizes in tumor compared to certain normal tissues. The mechanism of this is not well understood at this time, but has been documented in both animals &nd in patients. Selective retention of the photosensitizer in combination with focal light delivery to the involved area permits selective destruction of tumor with minimal effect on uninvolved normal tissue. Hematoporphyrin derivative photodynamic therapy may be clinically useful in a number of anatomic sites involved by tumor.